Method, arrangement, and pelletising plant

ABSTRACT

This invention concerns a method for the heating of a medium in a compartment  1  in which pellets  2  are arranged to be oxidised and sintered with the aid of the hot medium. The method comprises the introduction of a first medium  3  into the compartment  1  through an inlet  4  and the heating of the first medium  3  when it is present in the inlet  4.  The heating takes place through the use of a combustion arrangement  5,  or a part of such an arrangement, that is arranged in the inlet  4  and that comprises fuel. The heating, the use of the combustion arrangement  5,  comprises in turn the ignition of the fuel, combustion of the fuel whereby combustion heat is developed, and the transfer of the combustion heat to the first medium  3  that is present at the combustion arrangement  5  in the inlet  4.  The combustion arrangement  5,  or a part of it, is arranged in a region A in the inlet  4,  which in turn is arranged outside of the direct passage of the first medium in and through the inlet  4,  such that the ignition of the fuel, the combustion of the fuel and the transfer of combustion heat to the first medium  3  take place in this region A, followed by onwards transport of the heated first medium  3  from the region A into the compartment  1  through the inlet  4.  The invention concerns also an arrangement  7  and a pelletising plant  10.

TECHNICAL AREA

This invention concerns a method and an arrangement for the heating of amedium in a compartment in which pellets are arranged to be oxidised andsintered with the aid of the hot medium. The invention concerns also apelletising plant.

BACKGROUND

Iron ore concentrate, finely divided iron ore in powder form, from whichundesired components of the ore have been removed, is mixed with waterin a preparation plant in order subsequently to be processed in apelletising plant is known.

The ore concentrate is dewatered in the pelletising plant and mixed withvarious additives and binding agents, and rolled to small pellets. Thepellets are dried in a drying arrangement and heated in a compartmentsuch that the pellets are oxidised and sintered, caused to melttogether, one by one, to form final pellets, which maintain their shapeduring further transport. A cooling of the pellets subsequently takespace in a cooling arrangement. The pellets are now ready and can betransported onwards to the locations at which the ore is to be furtherrefined.

The use of an arrangement comprising an inlet connected to thecompartment for introduction of a medium through the inlet and into thecompartment is previously known. A combustion arrangement is arranged inthe inlet for heating the medium. The combustion arrangement comprisesfuel that, when the arrangement is in use, is ignited and combusted.Combustion heat is developed during the combustion of the fuel, whichheat is transferred to the medium that is present at the combustionarrangement in the inlet and that passes through the inlet on its way tothe compartment.

The heating of the pellets in a compartment is a very critical step inthe processing of the pellets and requires a relatively high temperaturein order to obtain a good result, in order for the pellets to bedurable.

DESCRIPTION OF THE INVENTION

One purpose of this invention is to offer a method, an arrangement and apelletising plant that ensure a desired temperature in a compartment inwhich pellets are oxidised and sintered.

This is obtained with a method having the technical features that aredescribed in claim 1, an arrangement with the technical features thatare described in claim 12 and a pelletising plant according to claim 21.

Preferred embodiments of the invention will be described below withreference to the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an arrangement according to the invention.

FIG. 2 shows a section through the arrangement in FIG. 1.

FIG. 3 shows a part of the combustion arrangement.

FIG. 4 shows a pelletising plant according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

A method and an arrangement according to this invention that will bedescribed below will have the same function and intention independentlyof whether it is a pelletising plant with iron pellets of whether it isa more general sintering plant in which ore concentrate is not formedinto pellets but where the ore concentrate is oxidised and sinteredwithout first being formed.

The term “pelletising plant” in the description below is to beinterpreted in its widest sense, which means that also a sintering plantis described by the term. The term “pellets” is also to be interpretedin its widest sense, such that also iron ore concentrate in randomaggregates in a sintering plant is described by the term “pellets”.

This invention concerns a method for the heating, in order to obtain aspecific temperature that has been determined in advance and is thedesired best temperature for the method, of a medium in a compartment 1in which pellets 2 are arranged to be oxidised and sintered with the aidof the hot medium.

The method comprises the introduction of a first medium 3 into thecompartment 1 through an inlet 4 and the heating of the first medium 3when it is present in the inlet 4. The heating takes place through theuse of a combustion arrangement 5, or a part of such an arrangement,that is arranged in the inlet 4 and that comprises fuel. The heating,the use of the combustion arrangement 5, comprises in turn the ignitionof the fuel, the combustion of the fuel whereby combustion heat isdeveloped, and the transfer of the combustion heat to the first medium 3that is present at the combustion arrangement 5 in the inlet 4.

The combustion arrangement 5, or a part of it, is arranged in a region Ain the inlet 4, which in turn is arranged outside of the direct passageof the first medium in and through the inlet 4, such that the ignitionof the fuel, the combustion of the fuel and the transfer of combustionheat to the first medium 3 all occur in this region A, followed byonwards transport of the heated first medium 3 from the region A intothe compartment 1 through the inlet 4. See FIGS. 1 and 2.

The arrangement of the combustion arrangement 5, or at least a part ofit, in the relatively undisturbed region A in the inlet 4 but outside ofthe direct passage of the medium in the inlet means that the ignitionand combustion of fuel take place in a region that is not directlyinfluenced, disturbed, by the medium, the first medium 3 that passes inthe inlet 4 on its way towards the compartment 1 in which the pellets 2are located.

When the combustion arrangement 5 is arranged outside of the directpassage of the first medium in the inlet 4, the combustion of the fueltakes place with a lower volume of air than that which has been usedpreviously. Also, the temperature of the first medium will be somewhatlower than previously when the combustion arrangement was locateddirectly in the inlet 4 and in the direct pathway of the medium. Thisresults in a lower flame temperature.

This location of the combustion arrangement, and the combustion that isa result of this, result, in turn, in a low NOx level in the residualmedium that is removed from the compartment in which the pellets areoxidised and sintered.

The method comprises also the introduction of a second medium 6 in thedirect vicinity of the combustion arrangement 5, or a part of it, in theregion A where the ignition of the fuel, the combustion of the fuel takeplace and the transfer of the combustion heat to the second medium 6takes place, together with onwards transport of the second medium 6 intothe compartment 1 through the inlet 4.

The method comprises the mixture of the heated first medium 3 and theheated second medium 6 in the inlet 4 before or during its introductioninto the compartment 1, or both before and during this introduction.This takes place through the media 3 and 6 being transported in commonthrough the inlet 4 during a certain period so that the media havesufficient time to mix before, or just as, they are introduced into thecompartment 1.

It is appropriate to preheat at least one of the first medium 3 and thesecond medium 6 before it is or they are introduced into the inlet 4,into the compartment A. This increases and stabilises the temperature ofthe medium that is heated by the combustion arrangement and that entersthe compartment 1. The best result is obtained if the first medium 3 ispreheated to a higher temperature than the second medium 6, mostpreferably to a temperature in the interval 500-1500° C.

The introduction of the media 3 and 6 takes place continuously. It isappropriate to use air as medium since the oxygen in the air stimulatesand improves the combustion in the combustion arrangement 5, which inturn gives a more even result of the heating and a higher temperature ofthe medium that is introduced into the compartment 1.

At least one of the media 3 and 6 is heated directly at the combustionarrangement 5 through the combustion of the fuel. The fuel is combustedcontinuously, and it is appropriate to use oil or gas as fuel in thecombustion arrangement 5. Since oxidation and sintering are twoprocesses that take place continuously, it is advantageous that alsovarious process stages take place continuously. The use of air, oil andgas is easy and stable throughout the process, since it is easy tomeasure and use these substances in continuous processes.

The invention concerns also an arrangement 7 intended to be used for theheating of, for the acquirement of a high temperature of, a medium in acompartment 1 in which pellets 2 are arranged to be oxidised andsintered with the aid of the hot medium.

The arrangement 7 comprises an inlet 4 connected to the compartment 1for the introduction of a first medium 3 through the inlet 4 and intothe compartment 1.

The arrangement 7 comprises also a combustion arrangement 5 for theheating of the first medium 3 when it is present in the inlet 4, wherethe combustion arrangement 5 comprises fuel that, during the use of thearrangement 7, is ignited and combusted whereby combustion heat isdeveloped, and is transferred to the first medium 3 that is located atthe combustion arrangement 5 in the inlet 4. The inlet 4 comprises aregion A, arranged outside of the direct passage of the medium in andthrough the inlet 4, in which the combustion arrangement 5, or at leasta part of it, is arranged such that the ignition of the fuel, thecombustion of the fuel and the transfer of combustion heat to the firstmedium 3 all occur in this region A, followed by onwards transport ofthe heated first medium 3 from the region A into the compartment 1through the inlet 4.

This arrangement 7 makes it possible to carry out the method that hasbeen described above and it results also in the advantages of the methodthat have been described.

The inlet 4 comprises an extension 4.1 that originates at a protrudingpart of the inlet 4 and whose interior makes available the region A.Thus the inlet has a different design and arrangement of space thanthose previously known. The extension 4.1 gives the inlet 4 a longershape, and makes it possible to locate the combustion arrangement 5behind the passage of the first medium into and through the inlet 4 andinto a relatively calm region A.

The combustion arrangement 5, or at least a part of it, is arranged atthe innermost side 4.1 a of the extension, and faces principally awayfrom the connection of the inlet with the compartment 1.

The arrangement 7 comprises an intake 8 arranged in connection with theregion A through which a second medium 6 is introduced in the directvicinity of the combustion arrangement 5, or a part of it, in the regionA in which ignition and combustion of the fuel take place. The intake 8is arranged at the innermost side 4.1 a of the extension, and facesprincipally away from the connection of the inlet with the compartment1.

The combustion arrangement 5 comprises a component 5.1 that in turncomprises a nozzle 5.2 through which fuel is fed out into the combustionarrangement 5. The combustion arrangement 5 may comprise also anignition arrangement 5.3 that ignites the fuel. This is normally notnecessary, since the temperature in the inlet 4 is so high that the fuelis ignited without a special ignition arrangement. The component 5.1constitutes the part of the combustion arrangement 5 that is arranged inthe inlet 4, in the region A. See FIG. 3.

It is appropriate that the arrangement 7 comprise a preheatingarrangement 9 that heats at least one of the first medium 3 before it isintroduced into the inlet 4, and the second medium 6 before it isintroduced into the inlet 4, the region A.

The limiting parts of the arrangement, the parts that limit the inlet 4,the region A and the intake 8, among others, are principallymanufactured from tubular sheet metal, and the parts are lined withceramic material.

The invention concerns also a pelletising plant 10 comprising anarrangement 7 according to any one of claims 12-20. See FIG. 4.

The pelletising plant 10 is of the “straight grate plant” type, andcomprises a belt transporter 11 on which pellets 2 are transportedthrough the complete pelletising plant 10, a drying arrangement 12 inwhich the pellets 2 are dried and may optionally be preheated, anoxidation and sintering part 13 that comprises the compartment 1, and acooling arrangement 14 that follows this sintering part.

This description of different embodiments of the invention andalternative designs of its items and methods is not to be seen as alimitation of the invention: it is to be interpreted in its broadestmeaning in order not to limit unnecessarily the protective scopeaccording to the attached patent claims. Changes that lie within theexpertise of a person skilled in the arts lie within the protectivescope of the innovative concept. The various designs of items that aregiven in the description above can be used and combined freely, as longas the desired function is obtained.

1. A method for the heating of a medium in a compartment in which ironore pellets are arranged to be oxidised and sintered with the aid of thehot medium, the method comprising: introducing a first medium into thecompartment through an inlet connected to the compartment: heating thefirst medium in the inlet through the use of a combustion arrangement ora part thereof arranged in the inlet, wherein the combustion arrangementor a part thereof comprises fuel, where the use of the combustionarrangement or a part thereof comprises the ignition of the fuel,combustion of the fuel, whereby combustion heat is developed, andtransfer of the combustion heat to the first medium that is present atthe combustion arrangement or a part thereof; wherein the combustionarrangement or a part thereof is in a region in the inlet that, in turn,is arranged outside of the direct passage of the first medium in andthrough the inlet such that the ignition of the fuel, the combustion ofthe fuel and the transfer of combustion heat to the first medium takeplace in this region, followed by onward transport of the heated firstmedium from the region into the compartment through the inlet.
 2. Themethod according to claim 1, comprising the introduction of a secondmedium in the direct vicinity of the combustion arrangement or a partthereof in the region where the ignition of the fuel, the combustion ofthe fuel take place and the transfer of the combustion heat to thesecond medium takes place, together with onwards transport of the secondmedium into the compartment through the inlet.
 3. The method accordingto claim 2, comprising the mixture of the heated first medium and theheated second medium in the inlet (4) before or during its introductioninto the compartment, or both before and during this introduction. 4.The method according to claim 2, comprising the preheating of at leastone of the first medium and the second medium before it is or they areintroduced into the inlet.
 5. The method according to claim 3,comprising preheating of the first medium to a temperature that ishigher than that of the second medium.
 6. The method according to claim4, comprising preheating of the first medium to a temperature in theinterval 500-1500° C.
 7. The method according to claim 1, where theintroduction of the media takes place continuously.
 8. The methodaccording to claim 1, comprising the use of air as medium.
 9. The methodaccording to claim 1, comprising direct heating of the media duringcombustion of the fuel.
 10. The method according to claim 1, comprisingcontinuous combustion of the fuel.
 11. The method according to claim 1,comprising the use of oil or gas as fuel.
 12. An arrangement for theheating of a medium in a compartment in which iron ore pellets arearranged to be oxidised and sintered with the aid of the hot medium, thearrangement comprising; an inlet connected to the compartment for theintroduction of a first medium through the inlet and into thecompartment; a combustion arrangement or a part thereof that is arrangedin the inlet for the heating of the first medium in the inlet, whereinthe combustion arrangement or a part thereof comprises fuel that, duringthe use of the arrangement, is ignited and combusted, whereby combustionheat is developed, which combustion heat is transferred to the firstmedium that is present at the combustion arrangement or a part thereof;wherein the inlet comprises a region arranged outside of the directpassage of the medium in and through the inlet, in which the combustionarrangement or a part thereof is arranged such that the ignition of thefuel, the combustion of the fuel and the transfer of combustion heat tothe first medium all take place in this region, followed by onwardstransport of the heated medium from the region into the compartmentthrough the inlet.
 13. The arrangement according to claim 12, where theinlet comprises an extension that originates at a protruding part of theinlet the interior of which offers the region.
 14. The arrangementaccording to claim 13, where the combustion arrangement or a partthereof is arranged at the innermost side of the extension, and facesprincipally away from the connection of the inlet with the compartment.15. The arrangement according to claim 12 comprising an intake arrangedin connection with the region through which a second medium isintroduced in the direct vicinity of the combustion arrangement or apart thereof in the region in which ignition and combustion of the fueltake place.
 16. The arrangement according to claim 15, where the intakeis arranged at the innermost side of the extension, and facesprincipally away from the connection of the inlet with the compartment.17. The arrangement according to claim 12, where the combustionarrangement or a part thereof comprises a component that in turncomprises a nozzle through which fuel in the combustion arrangement orpart thereof is fed out and where the component constitutes that part ofthe combustion arrangement or a part thereof that is arranged in theinlet.
 18. The arrangement according to claim 15, comprising apreheating arrangement that heats at least one of the first mediumbefore it is introduced into the inlet and the second medium before itis introduced into the inlet.
 19. The arrangement according to claim 12,where the limiting parts of the arrangement are principally manufacturedfrom tubular sheet metal.
 20. The arrangement according to claim 18,where the parts are lined with ceramic material.
 21. A pelletising plantcomprising an arrangement according to claim
 12. 22. The pelletisingplant according to claim 21 of the straight grate plant type,comprising: a belt transporter on which the pellets are transportedthrough the pelletising plant; a drying arrangement in which the pelletsare dried and may optionally be preheated, and an oxidation andsintering part that comprises the compartment and a cooling arrangementthat follows this compartment.